The known biopsy needle devices, to which will be shortly referred to as biopsy needles in the following description, comprise a needle consisting of a cannula, holding a slidable stem inside it. The distal end of said stem projects from the cannula distal end, and can arrange a portion of an organ to be sampled, after it has been cut from a guillotine-like point, located at the cannula distal end, because of the mutual approach of said distal ends The biopsy needles are then based on the principle of cutting a pre-defined organ portion by inserting them into the organ to be analysed, then arranging the cut tissue portion in the cavity which is comprised between the stem and the cannula, when this latter slides on the same stem.
The currently known biopsy needles are manually activated. Their cannula is locked to the needle support, while the stem proximal end is slidably supported by a movable assembly, fit to move the stem distal end with respect to the same end of the cannula.
The movable assembly stroke is adjustable in order to cut a pre-defined amount (in length) of the tissue sample to be taken.
Said manually activated needles are reasonably simple devices, but they lack in accuracy during the needle positioning and tissue sampling phases: in fact, it is difficult for an operator to coordinate by hand the mutual sliding of the needle stem and cannula, when both are independently movable and when the same operator must hold both with his hands.
Some biopsy needles which are automatically or semi-automatically operated are also known. They are manually pre-charged, and then inserted near the sampling area. They are then able to automatically carry out a first operating phase, wherein the distal stem cavity is ejected out of the cannula, and then a second operating phase, wherein a portion of tissue occupying the said cavity is cut by means of a guillotine-like effect when the cannula slides on the stem, until the cavity is totally enclosed into the cannula. The aforesaid needles can also work in a semi-automatic way, by executing the above described second operating phase not automatically, but by activating a manual control. This latter normally unlocks a locking member, which prevents said second phase from being activated.
In said biopsy needles the stem and cannula are supported each one by a respective assembly. Moreover, they are subject to elastic reaction forces, which are normally supplied by suitably arranged springs, in order to "charge" the needle, and then to be able to automatically or semi-automatically "shoot" with the same needle.
In the "charge" phase the stem cavity is placed inside the cannula, and the distal ends of said stem and cannula are held as close as possible to the needle body. This normally consists of a box-shaped case, which slidably supports the whole needle. It also contains the movable assemblies, the charge springs and further accessory members, e.g. safety devices fit to prevent any accidental needle "shooting". During said charging, phase the above safety devices are automatically connected, and some suitable springs are pre-charged in order to enable the needle for shooting.
During the shooting phase, after the security device has been disconnected and the needle has been put close to the organ to be analysed, it is possible, by operating the shooting "trigger", to eject the stem and then the cannula. This takes place because the springs acting on their respective movable assemblies are sequentially discharged. As described above, the shooting phase can take place in a semi-automatic way, by ejecting only the stem first, and then ejecting the cannula, after its locking device has been disconnected
A known kind of biopsy needle is charged by lifting from the needle body an element hinged thereon. Said element is connected to a mechanism operating on the springs to be charged, which is able to automatically insert the safety device, once the needle reaches its wide apart position, with respect to the same needle body.
In a further kind of known biopsy needle, the shooting springs are charged by mutually rotating two box-shaped cases, by means of a spring charging mechanism, which is operated by a plurality of helical guides. This kind of needle also comprises a shooting safety device, which is inserted once the charge operations have been completed.
A further known biopsy needle is charged by means of a cursor, which operates on the charging springs, arranged at the end of the biopsy needle body close to the outer needle portion. It is also axially slidable on that body. An operator charges the springs by pressing on the cursor head. This furthermore allows the safety device to be inserted.
The known biopsy needles have some common features, as the shooting "trigger", button or lever, which is placed near the free end of the needle body. They are also provided with means for adjusting the stem penetration depth and for defining the length of the tissue sample to be taken. A further common feature is that stem and cannula are charged simultaneously.
The main drawback of the above described biopsy needles is that their trigger can be placed only at the free end of the biopsy needle body, that is at a somewhat awkward position for an operator which wants to activate the needle during the shooting phase. In fact, the sample to be taken is at the opposite end with respect to said trigger, and operating this latter causes an axial force to be applied to the needle. This can displace the needle point from its correct position inside the sampled organ. In other words, the operator must hold the needle body with one hand, while operating the trigger with the other hand, in order to compensate the axial forces acting on the trigger and to prevent the needle point from being displaced. Thus, the operator cannot simultaneously use any other instrument (e.g. an ultrasound scanner probe), and the whole sampling operation decreases in accuracy. This lack of accuracy is especially evident when a small tissue area inside an organ must be sampled.
A further drawback is that the needle charge mechanisms are often very complex and of difficult operation, because operators have to study how the charging system works, and to acquire a good skill about its working.